Process for spinning wholly aromatic polyamide fibers



Dec. 3, 1968 H. s. MORGAN, JR

PUOCESS FOR SPINNING WHOLLY AROMATIC POLYAMIDE FIBERS Filed June 19,1964 R J M N 0 L 2% ER vO/M mM 5 MW E 2 5 H Y B ATTORNEY United StatesPatent 3,414,645 PROCESS FOR SPINNING WHOLLY AROMATIC POLYAMIDE FIBERSHerbert S. Morgan, Jr., Apex, N.C., assignor to Monsanto Company, St.Louis, Mo., a corporation of Delaware Filed June 19, 1964, Ser. No.376,363 17 Claims. (Cl. 264-210) ABSTRACT OF THE DISCLOSURE The solutionspinning of aromatic polyamides is improved by using a dry jet-wetspinning process wherein the polymer solution immediately afterextrusion is led through a gaseous medium for a short distance, about A;to 1 /2 inches, before entering the coagulation bath.

This invention relates to a process for the preparation of hightemperature resistant shaped and attenuated articles such as fibers,films, filaments, yarns and the like. More particularly, it relates to aprocess for the preparation of high strength thermally resistant fibers,filaments, films, and other shaped articles from Wholly aromaticpolyamide compositions.

There has recently arisen a need for shaped articles of improved hightemperature resistance. This need has 'been partially filled by theprovision of wholly aromatic polyamide compositions such as thoseprepared and described in US. Patents 3,006,899 to Hill et al.,3,049,518 to Stephens et al., 3,068,188 to Beste et 2.1., 3,079,219 toKing and 3,094,511 to Hill et al. Other wholly aromatic polyamidecompositions of unique structure such as those in our copendingapplications Ser. No. 222,930 to Preston, now US. Patent 3,240,760, Ser.No. 222,932 to Preston et -al., now US. Patent 3,232,910, Ser. No.298,467 to Smith et al., now US. Patent 3,354,125, Ser. No. 347,- 392 toPreston, now U.S. Patent 3,376,268 and Ser. No. 347,385 to Preston, nowUS. Patent 3,376,269, provide additional unique wholly aromaticpolyamide structures and compositions of very high thermal stability.All such Wholly aromatic polyamides may be generally described as havingno aliphatic linkages or segments in their regularly recurringstructural units. Thus included are all resonance-stabilized ringsystems whether benzene-aromatic or heteroaromatic. Examples of suchpolymers include:

poly (m-phenylene isophthalamide) {Zigiigil poly-N,N-m-phenylenebis(m-benzamide terephthalamide 3,414,645 Patented Dec. 3, 1968poly-N,N'-m-phenylenebis(m benzamide)-2,6-naphthylene dicarbonamidepoly-N,N'-m-phenylenebis (m-b enzamide) -4,4' -biphenyldicarbonamidepoly-4,4- bis (p-aminophenyl -2,2'-bithiazole is ophthalamide n L itsall @J poly-2,5 bis(p-aminophenyl)1,3,4oxadiazole isophthalamide l'i t iii I @-t fiQ poly-3,4'-diaminobenzanilide isophthalamide iii n L l andpoly-4,4-diaminobenzanilide terephthalamide i Q- Q- Q- l Because of theunique chemical structure of these wholly aromatic polyamidecompositions they have proven very ditlicult to process into shapedarticles. Their lack of any true melting point prevents satisfactorymelt extrusion. Their low solu'bilities in most conventional polyamidesolvents causes difficulty in dry or wet extrusion unless accessorysolubilizing agents such as salts of alkali or alkaline earth metals areadded to the solutions. This in turn requires exacting and extensiveafter treatments to remove the salts from the shaped articles andrequires stringent conditions of heat and attenuation to yieldsatisfactory fine structure in the finished article.

Accordingly, it is an object of this invention to provide shapedarticles of wholly aromatic polyamides.

Another object of the invention is to provide dense attenuatedstructures of unusually high crystallinity, orientation and thermalstability.

An additional object of the invention is to provide an improved modifiedWet extrusion process for preparing wholly aromatic polyamide filaments,fibers, films and other shaped articles.

Yet another object is to provide a dry jet-wet spinning process for theproduction of wholly aromatic polyamides of improved zero strengthtemperatures, high birefringence thermal stability and tenacity.

A further object is to provide a process for spinning wholly aromaticpolyamides which permits improved extraction of solvent and inorganicsalts from the polymer solution.

Other objects and advantages of the invention will become apparent fromthe description of the invention.

In accordance with this invention outstanding improvements are providedin the extrusion of wholly aromatic polyamides by using a dry jet-wetspinning process wherein the polymer solution immediately afterextrusion is led through a gaseous medium for a short distance, about A;to 1 /2 inches and preferably about from /4 to 1 inch before being ledinto the coagulating bath. The gaseous medium allows for instantaneousskin-core formation to begin before the fiber enters the coagulationbath. The expression dry jet-wet spinning refers to the fact that in theprocess of the invention the spinnerette or jet face is suspended abovethe coagulation bath liquid. After coagulation the fiber, depending onthe type of polymer used, is either washed or advanced to the next stepof the process. The remaining sequential steps are orientation, washing,a finish application if desired, drying, and an additional thermalstretching step referred to herein as a hot draw. Surprisingly,utilization of this technique leads to much improved extraction ofinorganic salts from the polymer solution, improved structuralproperties of the shaped objects, and excellent thermal stability.

The patents and patent applications previously mentioned disclosemethods for preparing the wholly aromatic polyamides of the invention.Generally the wholly aromatic polyamides of the invention may beprepared conveniently and preferably by combining an aromatic diacidchloride and an aromatic diamine in a lower alkylamide solvent toproduce the desired polyamide and the byproduct, hydrogen chloride. Thehydrogen chloride must be neutralized or removed to prevent its harmfuleffects to the resulting articles. Neutralization of the hydrogenchloride may be conveniently accomplished by adding an alkali, oralkaline earth, metal base to form a salt and water.

As a result of this neutralization reaction the polymers are furtherdissolved in the lower dialkylamide containing an amount of salt andwater which is proportional to the amount of hydrogen chloride formed inthe polymerization. This amount of salt ranges from about 1 to 8 percentbased on the solution weight of alkali or alkaline earth metal chloride.These solutions may also be prepared by stirring previously washedsalt-free polymer into a solvent consisting of a lower dialkylamide andfrom 1 to 8 percent of either an alkali or alkaline earth metal chlorideor bromide at a temperature of 60 to 90 C. Although it is not absolutelyessential it is preferred to add up to a total of 4 percent water tothese dopes to improve their stability.

It is desirable and convenient to use the same solvent forpolymerization and spinning. To this end lower alkylamides such asdimethylformamide and dimethylacetamide containing up to 10% by weightof dissolved metal salts such as lithium chloride, lithium bromide,calcium chloride, potassium chloride, zinc chloride and similar saltsare especially useful. Calcium chloride and lithium chloride arepreferred. Other solvents which may be used for spin solutionpreparation include trifiuoroacetic acid, dimethylsulfoxide,N-methyl-Z-pyrrolidone, and hexamethylphosphonic triamide. Thesesolvents usually have their solvency power enhanced by adding theaforementioned salts to the spin solution. Additional solvents may beobtained by using mixtures of two or more of these solvents.Concentrated sulfuric acid may also be used.

The polymer solution may be extruded at temperatures of 30 to 120 C. Thepolymer concentration may be increased or decreased within the preferredlimits of 10 to 30 percent to provide a suitable solution viscosity.Conversely, the viscosity of a given concentration may be adjusted byheating or cooling the solution briefly at a point just prior to theextrusion orifices. The spinnerette is preferably positioned with theface substantially parallel to the surface of the coagulation bath sothat the extruded solution passes through a short gaseous space beforeentering the coagulation bath. It is normally a simple matter to adjustthe jet to obtain the optimum distance and this distance will depend onthe concentration, viscosity, temperature and other spinning solutionconditions. Usually this distance will be from A; to 1 /2 inches,preferably about /2 an inch. However, this distance can be increased bytaking precaution that adjacent polymer streams do not come in contactwith and cohere to each other before entering the coagulation bath.

The temperature resistant wholly aromatic polyamides are convenientlyspun from about 10 percent to about 30 percent solutions, preferably 12to 20 percent solutions by weight, of the wholly aromatic polyamideshaving inherent viscosities of from about 0.6 to 3.0 or higher, andpreferably above about 1.2 as measured at 30 C. as a 0.5% solution indimethylacetamide containing 5% dissolved lithium chloride.

For best results the spinning variables should be correlated so thatless than one percent, if any, of the solvent based on the weight of thesolution is evaporated into the gaseous medium from the extruded stream.

It has been found that wholly aromatic polyamides with inherentviscosities of from about 0.6 to 3.0 or higher and preferably aboveabout 2.0 may be spun according to the invention by variations in thecoagulation bath and in the step immediately following coagulation.Where it is desirable to produce fibers for apparel and related end usessuch fibers should range in denier from about 1.0 to around 3.0 d.p.f.and should have tenacities of from about 2.5 to 5.0 g.p.d. In order toproduce fibers within these denier and tenacity ranges the inherentviscosity preferably should be about from 1.2 to about 2.0. When polymerwithin this inherent viscosity range is spun to fiber using a solventand water coagulation bath, back diffusion of water into the fibersoften occurs. In addition, excess swelling of the fiber results due tothe salt content normally present in the solvent system. The productobtained in such cases is a delustered yarn having brittleness, poortensile strength, large voids and granular structure. Instead of goingto more expensive and often less eifective solvents which do not need analkali or alkaline metal salt to enhance their solvency power a betterapproach is to change the composition of the coagulation bath to asolution of water and a polyalkylene glycol. Conversely, when it isdesirable to produce fiber for tire cord and other heavy industrial useshaving a tenacity of from about 5.5 to 8.5 g.p.d. and a denier of fromabout 6 to 8 d.p.f., the inherent viscosity should range from about 2.0to 2.4 or higher. Fiber of higher deniers (9 to 15 d.p.f.) may beconveniently formed from the higher molecular weight polymers. At thislevel of inherent viscosity the polyalkylene glycol coagulation bath isless efiicient resulting in sticking or fusion of filaments. In suchcases an aqueous coagulation bath is preferred.

The polyalkylene glycol coagulation bath comprises a mixture of fromabout to water by weight, and from about 30% to 5% of a polyalkyleneglycol. The term polyalkylene glycol as used in the specification andclaims refers to polyethers which may be derived from alkylene oxides orglycols and which may be rep esented by the formula HO(RO),,H in which Rstands for an alkylene radical such as methylene, ethylene, propylene,and butylene, and n is an integer of at least 4. The polyglycol maycontain inert substituents, for example methoxypolyethylene glycol, andmay consist of a mixture of polyalkylene glycols. These glycols havemolecular weights of from about 200 to 6000, preferably 600 to 2000.Although wide variations in the spin bath temperatures are permitted, itis preferred that the temperature range from about 5 C. to 60 C.,preferably from about C. to C.

The coagulation bath, for polymers having an inherent viscosity of about2.0 or higher, which is comprised of a mixture of from 0 to percent,preferably 0 to 10 percent of a dialkylamide in water, is highlyeffective even after a substantial concentration of metal salt builds upin the coagulation bath itself. It is convenient to provide freshsolvent-water mixture to the coagulation bath continuously whilewithdrawing continuously a portion of the bath containing solvent andmetal salt concentrations thus maintaining an essentially constantenvironment for coagulation. In order to assure constant coagulatingconditions in the bath, the solution is circulated and may be maintainedat a preferred concentration by the continuous addition of freshsolution or water while continuously removing an equal proportion of thespent solution. The temperature of the coagulation bath may be from 10C. to C., preferably 15 C. to 25 C., during coagulation. When coagulatedin the spin bath described, the wholly aromatic polyamide fibers of thisinvention have properties which permit their conversion by furtherprocessing into useful fibers with unique and novel properties.

The coagulation step in the process is followed by an orientation stepin which the fiber may be relaxed or stretched from less than one toabout four times its length in a conventional hot water or boiling waterstretch bath at a temperature of from about 50 C. to 100 C. Theorientation of the fiber may include washing the fiber on the take uproller or first godet which Withdraws the fiber from the coagulationbath and advances it toward the hot water stretch bath. This extraaqueous wash is desirable when very high salt concentrations are presentsuch as occur when highly insoluble polymers are being spun from saltcontaining solvents.

After orientation the fiber is washed with water at a temperature of 15C. to 65 C., with higher wash temperatures used when shorter washingtime is desired and lower wash temperatures when longer washing periodsare desired to remove substantially all traces of solvent and salts. Thewashed, oriented fiber is next passed through an optional aqueous finishbath where conventional lubricants and/or antistatic agents may beapplied. Of the types of finishes applicable, an antistatic type tocontrol the static electricity has been found the most valuable. Withoutan antistatic agent the dried fibers tend to repel one another and maybe ditficult to handle in further processing steps.

The fiber is dried in the conventional manner on steamheated cylindricalrolls or by any other suitable drying means. The temperature ispreferably maintained at from about 120 C. to 160 C.

Following the drying operation the fiber may be preheated by passingover a heated draw pin or through a heated enclosure such as an oven,furnace, or hot block slot where the fiber is continuously conditionedat about 300 C. to 500 C., preferably 400 C. to 450 C. The fiber is thendrawn from one to four times over a heated surface such as a hot shoetype heater at about 300 C. to 450 C. Alternately the fiber after dryingmay be advanced directly to the heated surface when a continuousspinning system is employed. When it is desirable to reduce shrinkageand further stabilize the fiber at high temperatures, preferably at350-450 C., the fiber may, after hot drawing, be passed over a heatedsurface several times by the use of small roller guides. The drawn (ordrawn and heat stabilized) fiber is finally collected on bobbins using aconventional take-up device.

As a further spinning aid when spinning fibers from polymers of thegeneral formula:

1.94-.. t1 LU U l such as poly N,N'-m-phenylenebis(m-benzamide)terephthalamide,

and poly N,N'-m-phenylenebis(m-benzamide) isophthalamide,

l 0 Q 0 (It it has been found desirable to include a dip bath with thefirst godet after the coagulation bath, containing a solvent extractionagent to improve the luster and other properties of the fiber. Suitableextraction agents which may be used include monohydroxy and polyhydroxycompounds such as methanol, ethanol, propanol, isopropanol, butanol,pentanol, ethylene glycol, propylene glycol, butylene glycol, glycerol,and mixtures of these compounds with up to 50 percent water. Otherextraction agents are polyalkylene glycols of 600 to 2000 molecularweight such as polyethylene glycol of 1000 molecular weight. Amides suchas dimethylacetamide, dimethylformamide, and urea mixed with 40 to 70%water may also be used. Other agents include acetonitrile (CH CN). Theseextraction agents are preferred when the polymer inherent viscosity isbelow about 1.90 and the desired denier is 6 d.p.f. or higher.

To further understand the invention reference will be made to theattached drawings that form part of the present application.

In the drawings, FIGURE 1 is a side elevational view partly in sectionshowing schematically an apparatus arrangement of the type which can beused in carrying out the process of the present invention.

FIGURE 2 shows a drawing of a photomicrograph cross-sectional view offibers obtained by the dry jet- Wet spinning technique.

FIGURE 3 shows a drawing of a photomicrograph cross-sectional view offibers obtained by a conventional wet spinning technique.

Referring now to FIGURE 1, 1 is the polymer solution hold tank. Polymersolution is pumped via pump 2 through filter 3 composed of two layers ofnylon, one layer of flannel, jet holder 4, and out of the spinnerette 5.The spinnerette is adjusted to the desired temperature by circulating aWarm fluid through the jet holder. The jet is normally of 10 to holes,each hole being 3-20 mils in diameter. The jet face is preferablypositioned parallel to the surface of the coagulation bath 7. Thepolymer solution is extruded downward and enters the coagulation bathpassing under spacer bar 6 positioned below the surface of the bathdirectly beneath the jet. The partially coagulated fiber continues anadditional distance in the bath, emerges and passes over the first godetrolls 8. First godet rolls 8 may have a dip bath containing a solventextraction agent through which the freshly coagulated yarn is furtherextracted before being drawn. The fiber is then fed through a hot orboiling water stretch bath 9 and over the draw wash rolls 10 where thefiber is washed with hot water. The fiber then passes through a finishbath 11 and on to drying rolls 12. After thorough drying is accomplishedthe fiber is fed directly over the hot pin 13 and is drawn by rolls 15over shoe 14. The pin is normally set at a temperature about 50 C. abovethe shoe temperature to insure adequate preheating of the yarn. If anoven is used as the preheater, the temperature within the oven should be50100 C. greater than the shoe temperature. Alternately the yarns may bepreheated only with the drier rolls. The drawn yarn is collected onbobbin 16 using a conventional take-up device.

In FIGURES 2 and 3 the contrast of fiber cross-sections clearly showsthe advantage of the process of the invention. The dry jet-wet spunfibers of FIGURE 2 have excellent clear internal structure, whereasthose of FIGURE 3, of wet spun fibers, contain numerous voids.

The preferred and optimum spinning conditions for a 6 d.p.f. fiber aresummarized in Table 1 as follows:

TABLE 1 Preferred Spinning condition operating Optimum ranges conditionsPolymer inherent viscosity. 1. 70-2. 50 2. 20 Polymer solids, percent15-22 20 Dope temperature at jet, C 40-130 70 Distance from jet fact tospin bath surface, inches 025-1. 50 0. 50 Spin bath comp., by volume:

Percent water 90-100 99 Percent solvent 10-0 1 Spin bath temp., C..."10-30 25 First godet speed, f.p m 12-150 34 Orientation stretch 88-2.80X 2.10X Wash water temp., 15- 60 Finish Finish concentration, percentby weight 0. -10 0 2.0 Washer to drier stretch 0.95-1.00 1. 0X Drierroll temp., C... 120-160 150 Drier speed, Lp 13-420 71. 2 Preheater oventemp 300-500 450 Shoe temp., C 300-450 375 Hot draw ratio 1. 0-4. 0X 1.70X Final Speed, f.p.m 16. 3-714 121 1 An article and/or lubricant.

The maximum operable hot draw is dependent upon the orientation stretchratio. The total draw from spinnerette or jet face to final takeup godetwill vary from about 2.0x to 12.0 T

The invention is further illustrated by the following examples which arepresented for illustrative purposes only and are not restrictive of theinvention. In the examples all percentages are given on a total solutionweight basis unless otherwise indicated. The examples employ fivedifferent wholly aromatic polymers comparing three different types ofspinning systems.

EXAMPLE I Poly N,N-m-phenylenebis(m-benzamide)2,6-naphthylenedicarbonamide waspolymerized as described in Ser. No. 222,930 to give a solutioncontaining 20 percent polymer, 3 percent lithium chloride, 1 percentwater and 76 percent dimethylacetamide with a viscosity of 17,280 poisesat 23.5 C. The solution was heated to 102 C. and dry spun into hot airin a foot tower using a 5 mil 14-hole spinnerette with an inlet airtemperature of 215 C., a spinning speed of 750 f.p.m. and a jet stretchof 7.82 The fiber was collected on a bobbin and then leached for twodays with four changes of deionized water at room temperature and atapproximately 12 hour intervals. The dried fiber at this point in theprocess contained about 4.5 percent dimethylacetamide. The fibers werethen unwound from the bobbin onto advancing rolls and passed at 141f.p.m. over a 12 inch hot shoe adjusted to 300 C., drawn 1.7 times andcollected on bobbins. This fiber had the properties shown in Table 2,which follows Example IX.

EXAMPLE II The polymer-solvent system employed in Example I was heatedto C. and used with a 10 hole, 5 mil spinnerette for wet spinning in toa 55 C. aqueous spin bath. After an immersion of 23 inches in the spinbath the fiber was advanced by drawing rolls which stretched the fiber1.13 times in the spin bath. From the spin bath the fiber was subjectedto an orientation stretch of 2.25 in a boiling water bath. The fiber wasnext advanced to a set of washer rolls and washed with 55 C. water.After washing a 5 percent antistatic finish dispersion was applied froman aqueous finish bath. After application of the finish the fiber wasadvanced over heated drier rolls, at a temperature of 135 C. where itwas drawn an additional 1.16 times and simultaneously dried. Afterdrying the fiber was passed over a 12 inch drawing shoe at 290 C. anddrawn by advancing rolls an additional 1.5 times. The fiber was thencollected on bobbins at a final spinning speed of 87.3 f.p.m. Theproperties of this fiber are shown in Table 2.

EXAMPLE III The polymer-solvent system employed in Example I was spun asshown in FIGURE 1 under the conditions prescribed in Table 1. Theproperties of the fiber are shown in Table 2.

EXAMPLE IV The conditions employed in Example III were followed inExample IV with the exception that the polymer employed was polyN,N-m-phenylenebis (m-benzamide) 4,4-biphenyldicarbonamide. Thepreparation of this polymer is described in Ser. No. 222,930 previouslymentioned. The properties of the fiber obtained are shown in Table 2.

EXAMPLE V The conditions employed in Example III were followed in thisexample with the polymer used being poly N,N'- m phenylenebis(mbenzamide) terephthala-mide. The preparation of this polymer isdescribed in Ser. No. 222,932. The properties of the fiber obtained areshown in Table 2.

EXAMPLE VI The conditions employed in Example I were followed in ExampleVI with the following exceptions. The polymer, poly(m-phenyleneisophthalamide), was prepared in accordance with U.S. 3,006,899 to givea dimethylacetamide solution containing 20 percent polymer and 3 percentlithium chloride with a viscosity of 5,760 poises at 25 C. The solutionwas heated to C. A 6 mil l4-hole spinnerette, and an inlet airtemperature of 173 C. was used. The spinning speed was 132 f.p.m., jetstretch 4.58 and the fibers were drawn 5.62 times over a hot shoeadjusted to 325 C. The properties of this fiber are shown in Table 2.

EXAMPLE VII EXAMPLE VIII A solution containing 1 8 percent ofpoly-3,4'-diaminobenzanilide isophthalamide in dimethylacetamidecontaining 3 percent dissolved lithium chloride was prepared.

9 The solution was heated to 65 C. and dry spun in a 15 foot spinningtower using a mil-8 hole jet. A jet stretch of 3.7 times, a spinningspeed of 225 f.p.m., an entrance air temperature of 190 C., and an exitair temperature of 165 C. were employed. Fiber was wound on a perforatedbobbin and continuously leached for 24 hours with water at roomtemperature. After leaching the fiber was air dried at room temperature.The dried fiber was then unwound from the bobbin onto advancing rollsand passed at 123 f.p.m. through a 12 inch oven set at 425 C. and thenimmediately drawn 1.7 times over a 12 inch shoe adjusted to 425 C. Afterdrawing the fiber was collected on bobbins. The properties of this fiberare recorded in Table 2.

EXAMPLE IX A solution containing 18 percent ofpoly-3,4'-diaminobenzanilide terephthalamide in dimethylacetamidecontaining 3 percent dissolved lithium chloride was prepared and spun asdescribed in FIGURE 1 under the conditions prescribed in Table 1. Theproperties of this fiber are shown in Table 2 which follows:

jet stretch for the wet spinning technique was 1.38 For the dry jet-wetspinning method a jet stretch of 7.3x was obtainable. The ability tospin with this increased latitude in jet stretch makes the dry jet-wetspinning process more flexible and convenient to employ than the wetspinning system. It also facilitates a higher degree of orientation andcrystallinity in the finish fiber, and enables a much wider range offiber denier tobe spun conveniently.

EXAMPLE XII TABLE 2.PROPERTIES OF FILAMENTS Example I II III IV V VI VIIVIII IX Denier per filament" 2. 1 5. 0 10. 4 8. 2. 9 1. 5 1. 7 2. 5 2. 6Tenacity (g./d.) 3. 2 2. 0 6.10 6.10 6.0 6. 50 4. 0 4.0 3.6 Elongation(percent) 19. 7 16. 5 15. 1 20. 8 23. 3 33. 0 1 16. 7 29 5. 6 Refractiveindex (parallel). 1. 785 1. 930 1. 855 1. 843 l. 792 1. 812 1. 820Birefringence 0. 100 0. 274 0. 222 0. 184 0. 139 0. 154 0. 165 250 Zerostrength temp. 0.)--. 302 320 515 500 500 470 515 325 500 Li content(p.p.m.) 85 0.5 3.4 38. 3 15.8 0. 24 2.4

1 Bundle breaks, elongation.

2 Refractive index (and birefringence) data are not reproducible due tothe presence of large voids and a granular structure.

In the table birefringence data were obtained by measuring the paralleland perpendicular refractive indices in plane cross-polarized lightusing the Becke line technique. Birefringence is calculated from therefractive indices. Zero strength temperature test was determined byheating a yarn at 0.1 gram per denier load in a nitrogen atmosphere. Thetemperature was raised at a rate of 5 C. per minute until the samplebroke. The temperature at which the sample broke was taken as the zerostrength temperature.

The superiority of the dry jet-wet spinning technique over dry spinningis obvious on the basis of ease and completeness of salt removal,superior orientation, and crystallinity in the drawn fibers. In terms ofwet spinning versus dry jet-wet spinning another distinction is readilydemonstrable. The same polymer as described in Example III was dryjet-wet spun except that the jet stretch was retricted to 1.31 times.After collecting fiber under the stable dry jet-Wet spinning conditions,the spinnerette was lowered into the spin bath and the sample wet spunwithout changing any conditionother than submerging the spinnerette. Thefiber cross section obtained by the dry jet-wet spinning technique isshown in FIGURE 2. The cross section obtained by the wet spinningtechnique is shown in FIGURE 3. The dry jet-wet spun fiber was void freeand is much preferred over the highly voided structures shown in FIGURE3. During the dry jet-wet spinning the distance from the face of thespinnerette to the point along the thread line where the fiber appearedto be coagulated or delustered was approximately 7 inches. This samepoint was observed only 0.5 inch from the spinnerette face with thefiber when wet spun.

EXAMPLE XI The spinning conditions employed in Example X were repeatedwith the exception that the maximum jet stretch was determined for boththe dry jet-wet spinning and wet spinning techniques. The maximum jetstretch is defined as the maxi-mum stretch which may be applied betweenthe spinerette face and the first advancing rolls without causing thebreaking of filaments. The maximum EXAMPLE XIII TABLE 3 Dry heat Exampleshrinkage at (percent) 1 The dry heat shrinkage was obtained bymeasuring the decrease in a 20 cm. length of yarn after five minutecontact with a heated metal surface. The percent shrinkage wascalculated from the change in length.

EXAMPLE XIV A solution was prepared containing 20 percent of polyN,N-m-phenylenebis(m-benzamide) terephthalamide (with an inherentviscosity of 1.92), 3 percent lithium chloride, 1 percent water and 76percent dimethylacetamide. Additional lithium chloride was added toincrease the concentration to 6 percent lithium chloride. The solutionwas heated to 80 C. and spun as in Example III with the followingexceptions. The coagulation bath was comprised of 80 percent water and20 percent polyethylene glycol of 1000 average molecular weight at atemperature of 20 C. The fiber was given a preliminary wash on the firstgodet after emerging from the coagulation bath and prior to theorientation stretch. Spinning stability was good and a 5.1 d.p.f. fiberwas obtained with a tenacity of 5.0 g.p.d., 29.1 percent elongation,modulus of 82 g./d. and a zero strength temperature of 511 C.

1 l EmMPLE xv A solution of poly N,N-m-phenylenebis(mbenzamide)4,4-biphenyldicarbonamide was prepared and spun as in Example XIV. An8.3 d.p.f. fiber having a tenacity of 6.1 g.p.d., elongation of 20.8percent and a modulus of 82 g.p.d. was obtained.

EXAMPLE XVI A solution of poly N,N-m-phenylenebis(m-benzamide)2,6-naphthylene dicarbonamide was prepared and spun as in Example XIV. A2.2 d.p.f. fiber with a tenacity of 7.0 g.p.d., elongation of 16.6percent, modulus of 118 g.p.d. and a zero strength temperature of 506 C.was obtained.

A study of these examples will Show that the process of the inventionproduces fibers of greatly improved properties over the prior art. Thezero strength temperature of fibers produced by the dry jet-wet spinningprocess is consistently higher than that of fibers produced by alternateprocesses, ranging mostly from about 500 C. to around 525 C. The whollyaromatic fibers described in the prior art all have zero strengthtemperatures well below 500 C. and in most cases below 450 C. Dry heatshrinkage and the occurrence of voids are substantially improved. Thedry heat shrinkage at 400 C., shown by Table 3, is especiallynoteworthy, showing an improvement for the same fiber in Examples VI andVII of from about 80 to about percent shrinkage. Birefringence valuesare also vastly improved with all fibers produced by the process of theinvention having a birefringence greater than 0.150.

EXAMPLE XVII A solution of percent of 2.38 inherent viscosity polyN,N-m-phenylenebis(m-benzamide) 2,6-naphthalene dicarbonamide indimethylacetamide containing 5 percent dissolved lithium chloride wasspun under the conditions set forth in Table 1. The fiber was given a3.14 jet stretch, 2.55 X orientation stretch and finally hot drawn 1.27at 350 C. The tensile properties of the fiber were 11.6 d.p.f., 5.86g.p.d. tenacity, 14.10 percent elongation and a modulus of 134.0 g.p.d.

EXAMPLE XVIII This example shows various dehydrating or solventextraction agents which are useful in improving the spinning of polymersof the general formula IHN/\-E NH Na salt ill LU l l @1 Samples ofpoly-N,N'-m-phenylenebis(m-benzamide) terephthalamide of 1.90 inherentviscosity were spun under the conditions described in Table 1, exceptthat the orientation bath temperature was lowered to about C. with theaddition of a dip bath on the first godet using the following solventextraction agents:

In each case the use of the extraction agent achieved a uniform fibercollapse, elimination of any tendency for fiber ccmentation, improvedyarn drying rate on the dryer rolls, more lustrous yarns, and a broaderrange of spinning variables which could be used without causingborderline performance.

The advantages of wholly aromatic polyamide fibers prepared by theprocess of this invention over such fibers prepared by either dry or wetspinning processes are obvious. The process is outstanding and unusualon the basis of the simplicity, ease of operation, and economicallyattractive use of conventional fiber spinning equipment. The processavoids explosion hazards and flammability and, in some cases, hazardousand ineffective leaching operations characteristic of other processesreported in the prior art. The range of fiber orientation combinationsavailable is an additional attractive feature of the process. The fibersproduced according to the process of this invention have excellentstrength, outstanding thermal stability and are highly lustrous.

Fibers with such properties are particularly useful in shaped articleswhich find applications in uses requiring exposure to elevatedtemperatures. In the form of fibers, filaments and other shaped articlesthey are useful in applications such as electrical insulations,industrial filters, conveyor belts tire cord, heat resistant parachutes,protective clothing and the like.

The foregoing detailed description has been given for clearness ofunderstanding only, and unnecessary limitations are not to be construedtherefrom. The invention is not to be limited to the exact details shownand described since obvious modifications will occur to those skilled inthe art, and any departure from the description herein that conforms tothe present invention is intended to be included within the scope of theclaims.

I claim:

1. A process for the preparation of shaped articles from wholly aromaticpolyamide solutions comprising the steps of:

(1) extruding the solution in a downward direction into a stream byforcing the solution through a shaped orifice at a temperature of fromabout 30 C. to 120 C. into a gaseous medium in which only a small amountof the solvent is evaporated from the stream;

(2) directing the stream through the medium for a short distance andinto a coagulating bath comprising a liquid containing at least 60percent water that is a precipitant for the polymer and an extractantfor the solvent;

(3) withdrawing the thus-formed article from the coagulating bath;

(4) passing the article through a wash liquid while stretching same toorient the polymer molecules thereof;

(5) washing the article;

(6) drying the article;

(7) and passing the article through a heated environment under tensionto produce a shaped article.

2. A process for the preparation of fibers from wholly aromaticpolyamide solutions, containing from 10 to 30 percent polyamide bysolution weight, comprising the steps of:

(1) extruding the solution in a downward direction into a stream byforcing said solution through a shaped orifice at a temperature of fromabout 30 C. to 100 C. into a gaseous medium in which only a small amountof the solvent is evaporated from the stream;

(2) directing the stream through the medium a distance of from inch to1% inches and into a coagulating bath comprising a liquid containing atleast 60 percent water that is a precipitant for the polymer and anextractant for the solvent at ambient tem peratures;

(3) withdrawing the thus-formed fiber from the coagulating bath;

(4) passing the fiber through a wash liquid comprising boiling waterwhile stretching same from less than 1 to 4 times to orient the polymermolecules thereof;

(5 washing the fiber with water at a temperature of from 40 C. to C.;

(6) drying the fiber at a temperature of from 120 to (7) and passing thefiber through a pre-heated environment at a temperature of from 400 C.to 480 C. under sufiicient tension to elongate said fiber one to threetimes its length.

3. A process for the preparation of fibers from a wholly aromaticpolyamide solution, containing from 10 to 30 percent polyamide bysolution weight dissolved in a lower dialkylamide containing from 1percent to 8 percent of a (6) Washing the fiber with a second washliquid comprising water at a temperature of from about 50 C. to 65 C.;

(7) drying the fiber at a temperature of from about 120 C. to about 160C.;

(8) and advancing the fiber through a heated environment under tensionto produce a wholly aromatic polyamide fiber.

10. A process for the preparation of fibers from wholly aromaticpolyamide solutions, containing from to 22 metal halide selected fromthe group consisting of alkali and alkaline earth metal halides,comprising the steps of:

(1) extruding the solution in a downward direction into 'a stream byforcing said solution through a shaped orifice at a temperature of from40 C. to 100 C. into a gaseous evaporative medium in which only a smallamount of the lower dialkylamide is evapo rated from the stream;

(2) directing the stream through the medium for a distance of from A ofan inch to 1 inch and into a coagulating bath comprising from about 1percent to 10 percent of a lower dialkylamide and from 90 percent to 99percent of water at ambient temperatures;

(3) withdrawing the thus-formed fiber from the coagulating bath at arate suflicient to impart a jet stretch of from about 2 to 7 times itslength;

(4) passing the fiber through a wash liquid comprising boiling waterwhile stretching same from less than 1 to 4 times its length to orientthe polymer molecules thereof;

(5) washing the fiber with water at a temperature of from 40 C. to 80C.;

(6) drying the fiber at a temperature of from 120 C.

to 160 C.;

(7) and passing the fiber through a pre-heated enclosure at atemperature of from 400 C. to 480 C.

under sufiicient tension to elongate said fiber 1 to 3 times its length.

4. The process of claim 3 wherein the lower dialkylamide isdimethylacetamide.

5. The process of claim 3 wherein the lower dialkylamide isdimethylformamide.

6. The process of claim 3 wherein the alkali metal halide is lithiumchloride.

7. The process of claim 3 wherein the alkaline earth metal halide iscalcium chloride.

8. The process of claim 3 wherein the alkali metal is lithium bromide.

9. A process for the preparation of fibers from wholly aromaticpolyamide solutions containing from 10 to 30 percent polyamide bysolution weight and having an inherent viscosity of from about 1.2 to2.0 comprising the steps of:

(1) extruding the wholly aromatic polyamide solution in a downwarddirection into a stream by forcing the solution through a shaped orificeat a temperature of from about 30 to 120 C. into a gaseous medium inwhich only a small amount of the solvent is evaporated from the stream;

(2) directing the stream through the medium a distance of from Ms inchto 1 /2 inches and into a coagulating bath maintained at a temperatureof from about 10 C. to 30 C., comprising a mixture of from about 70% to95% water by weight, and from about 30% to 5% of a polyalkylene glycol;

(3) withdrawing the thus-formed fiber from the coagulating bath;

(4) moving the fiber through a wash liquid comprising water at atemperature of from about 15 C. to 60 C.;

(5) passing the fiber through a hot aqueous bath while stretching sameto orient the polymer molecules thereof;

percent polyamide by weight dissolved in a solvent and having aninherent viscosity of from about"2.0 to 3.0, comprising the steps of:

(1) extruding the wholly aromatic polyamide solution in a downwarddirection into a stream by forcing the solution through a shaped orificeat a temperature of from about 30 to 120 C. into a gaseous evaporativemedium in which only a small amount of the solution preparation solventis evaporated from the stream as a gas;

(2) directing the stream through the medium for a short distance andinto a coagulating bath comprising from about 1 percent to 10 percent ofthe solvent and from 90 percent to 99 percent of water at ambienttemperatures;

(3) withdrawing the thus-formed fiber from the coagulating bath;

(4) passing the fiber through a boiling water bath while stretching sameto orient the polymer molecules thereof;

(5) washing the fiber with water at a temperature of from about 15 C. to65 C.;'

( 6) drying the fiber;

(7) and advancing the fiber through a heated environment under tensionto produce a wholly aromatic polyamide fiber.

11. A process for the preparation of poly N,N'-mphenylenebis(m-benzamide) 2,6 naphthylenedicarbonamide fibers comprising the stepsof:

(1) extruding a solution of 15 to 22 percent by solution weight of polyN,N'-m-phenylenebis (m-benzamide)-2,6-naphthylenedicarbonamide,dissolved in a solvent comprising 70 to percent dimethylacetamide. 1 to10 percent lithium chloride and 1 to 5 percent water, in a downwarddirection into a stream by forcing the solution through a shaped orificeat a temperature of from about 30 C to 120 C. into a gaseous evaporativemedium comprising air in which only a small amount of the solvent isevaporated from the stream as a gas;

(2) directing the stream through the air for a distance of inch to 1inch and into a coagulating bath comprising percent to 99 percent ofwater and 1 percent to 10 percent of the solvent;

(3) withdrawing the thus-formed fiber from the coagulating bath;

(4) passing the fiber through a wash liquid comprising boiling waterwhile stretching same from 0.88 to 2.80 times its length to orient thepolymer molecules thereof;

(5 washing the fiber with water at a temperature of from 40 C. to 80 C.;

(6) drying the fiber at a temperature of from about C. to about C.

(7 and subjecting the fiber to a hot draw by advancing the fiber througha preheater oven at a temperature of from 300 C. to 450 C., then over ashoe heated to a temperature of from 300 C. to 450 C. while stretchingthe fiber from 1 to 4 times its length.

12. A- process for the preparation ofpoly-N,N'-mphenylenebis(m-benzamide)terephthalamide fibers comprisingthe steps of:

(1) extruding a solution of from 15 to 22 percent by solution weight ofpoly-N,N-m-phenylenebis(m- 15 benzamide)terephthalamide, dissolved in asolvent comprising 85 to 98 percent dimethylacetamide, 1 to 10 percentlithium chloride and 1 to percent water, in a downward direction into astream by forcing the solution through a shaped orifice at a temperatureof from about 30 C. to 120 C. into a gaseous evaporative mediumcomprising air in which only a small amount of the solvent isevaporative from the stream as a gas;

(2) directing the stream through the air for a distance (5 washing thefiber with water at a temperature of 1 6 prising 90 percent to 99percent of water and 1 percent to percent of the solvent;

(3) withdrawing the thus-formed fiber from the coagulating bath;

(4) passing the fiber through a wash liquid comprising boiling waterwhile stretching same from 0.88 to 2.80 times its length to orient thepolymer molecules thereof;

(5) washing the fiber with water at a temperature of from 40C. to 80C.;

Of 1A inch t0 1 inch and into a coagulating bath COm- 10 (6) drying thefiber at a temperature of from about prising 90 percent to 99 percent ofwater and 1 per- 120 C. to about 160 C.

cent to 10 percent of the solvent; (7) and subjecting the fiber to a hotdraw by advancing (3) withdrawing the thus-formed fiber from the cothefiber through a preheater oven at a temperature agulating bath; of from200 C. to 450 C. then over a shoe heated (4) passing the fiber through awash liquid comprising to a temperature of from 300 C. to 450 C. whileboiling water while stretching same from 0.88 to stretching the fiberfrom 1 to 4 times its length.

2.80 times its length to orient the polymer molecules 15. A process forthe preparation of poly-N,N'-mthereof; phenylenebis (m-benzamide)4,4'-biphenyldicarbonamide (5) washing the fiber with water at atemperature of fib r comprising th steps of;

from 40 C. to 80 C.; (1) extruding a solution of 15 to 22 percent bysolu- (6) drying the fiber at a temperature of from about tio weight ofpoly N,N-m-phenylenebis (tn-benz- 120 C. to about 150 C.; amide)4,4-biphenyldicarbonamide, dissolved in a (7) and subjecting the fiberto a hot draw by advancsolvent comprising 85 to 98 percentdimethylacetaing the fiber through a preheater oven at a temp ra- 5mide, 1 to 10 percent lithium chloride and 1 to 5 perture of from 300 C.to 450 C., then over a shoe cent water, in a downward direction into astream heated to a temperature of from 300 C. to 450 C. by forcing thesolution through a shaped orifice at a while stretching the fiber from 1to 4 times its length. temperature of from about to 120 C. into a 13. Aprocess for the preparation of poly(m-phenylgaseous evaporative mediumcomprising air in which eneisophthalamide) fibers comprising the stepsof: 3 only a small amount of the solvent is evaporated (1) extruding asolution of 15 to 22 percent by solufrom th tr a as a gas;

tion weight of poly(rn-phenyleneisophthalamide) (2) directing the streamthrough the air for a distance dissolved in a solvent comprising 85 to98 percent (11- of 1A inch to 1 inch and into a, coagulating bathcornmethylacetamide, 1 to 10 percent lithium chloride prising 90 percentto 99 percent of water and 1 perand 1 to 5 percent water in a downwarddirection cent to 10 percent of the solvent;

intO a Stream y forcing the Solution through a (3) withdrawing thethus-formed fiber from the coagshaped orifice at a temperature of fromabout 30 C. ulating b th;

to 120 C. into a gaseous evaporative med m C m- (4) passing the fiberthrough a wash liquid comprising p g air in which y a Small amount ofthe boiling water while stretching same from 0.88 to vent is evap rat dfr m th stream as a g 2.80 times'its length to orient the polymermolecules (2) directing the stream through the air for a distance th f;

Of 141 inch to 1 inch and into coagulating bath (5) washing the fiberwith water at a temperature of prising 90 percent to 99 percent of waterand 1 perf 40C to 80C.;

cent to 10 percent of the solvent; (6) drying the fiber at a temperatureof from about (3) withdrawing the thus-formed fiber from the co- 120 C,t b t 160 C,

agulating bath; (7) and subjecting the fiber to a hot draw by advanc- Ps g th r through a wash liquid comprising the fiber through a preheateroven at a temperaing boiling water while stretching same from 0.88 t eof fro 300 C t 450 c h over a h to 2.80 times its length to orient thepolymer moleheated to a temperature of from 300 C. to 450 C.

cules thereof; while stretching the fiber from 1 to 4 times its length.

16. A wholly aromatic polyamide fiber produced acfrom 40 C. to 80 C.;

(6) drying the fiber at a temperature of from about 120 C. to about 160C.;

(7) and subjecting the fiber to a hot draw by advancing the fiberthrough a preheater oven at a tempera ture of from 200 C. to 450 C. thenover a shoe cording to the process of claim 1, having a birefringence ofat least 0.150 and a Zero strength temperature of at least 500 C.

17. A process for the preparation of p0ly-N,N-rnphenylenebis(m-benzamide) terephthalamide, fibers of at least 6 d.p.f. comprisingthe steps of:

heated to a temperature of from 300 C. to 450 C. while stretching thefiber from 1 to 4 times its length.

C to 120 C. into a gaseous evaporative medium comprising air in whichonly a small amount of the solvent is evaporated from the stream as agas; (2) directing the stream through the air for a distance of A inchto 1 inch and into a coagulating bath com- (1) extruding a solution offrom 15 to 22 percent by solution weight of poly-N,N-m-phenylenebis(mbenzamide) terephthalamide having an inherent vis- 14. A process forthe preparation of poly-3,4'-diamino- 6O benzanilide isophthalamidefibers comprising the steps coslty above about dls solved m a f of:comprising to percent dimethylacetamide, 1

(1) extruding a solution of 15 to 22 percent by solu- 33 g? gi s ggxgg gggggis fi to tion weight of poly-3,4'-diaminobenzanilide isophthalrforcing the Solution through a p i i g Z amide dissolved in a solventcomprising to 98 temperature of from about C to C into percentdimethylacetamide, 1 to 10 percent lithium a gaseous medium comprisingair'in which o'nly a chloride and 1 to 5 percent water, In a d wn smallamount of the solvent is evaporated from the direction into a stream byforcing the solution through Stream as a a shapfid Oflfice at atemperature of from about 70 (2) directing the stream through the airfor a distance of 4 inch to 1 inch and into a coagulating bathcomprising percent to 99 percent of water and 1 percent to 10 percent ofthe solvent;

(3) withdrawing the thus-formed fiber from the coagulating bath;

l 7 1 8 (4) passing the fiber through a dip bath containing a ing thefiber over a shoe heated to a temperature of solvent extraction agentselected from the group confrom 300 C. to 450 C., while stretching thefiber sisting of hydroxy compounds containing one to three from 1 to 4times its length.

hydroxy] groups and up to 6 carbon atoms, polyalkylene glycols of 600 to2000 molecular Weight, mix- References Cited tures of amides with fromto percent water, UNITED STATES PATENTS and mixtures of the hydroxycompounds with up to 3 210 452 10/1965 Howard 264 205 50 percent water,then through a wash liquid com- 3068188 12/1962 Beste at 26O 30 2prising water at 50 C. While stretching the fiber 3:079:219 2/1963 Kingfrom 1.10 to 2.80 times lts length to orlent the 10 3,080,210 3/1963Ucci 264 182 polymer molecules thereof,

(5) washing the fiber with water at a temperature of FOREIGN PATENTSfrom 40C. to C.; 240,201 8/1962 Australia.

t 5 2 iggi z f 3; gtemperature from abou JULIUS FROME, Primary Examiner.

1o (7) and subjecting the fiber to a hot draw by advanc- H. H. MINTZ,Assistant Examiner.

